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Abstract

Blueberry is clonally propagated by hardwood and softwood cuttings, and by micropropagation. Zimmerman and Broome (7) reported 22.8 µm 1H-indole-3-acetic acid (IAA) plus 73.8 µm N-(3-methyl-2-butenyl)-1H-purin-6-amine (2ip) to be optimal for axillary shoot proliferation. Lyrene (4) found that 28.5 µm IAA added to medium containing 73.8 µm 2ip had no effect on shoot multiplication. Although lowbush blueberries produced increasingly more shoots as 2ip concentrations increased from 0 to 147.6 µm (2), three highbush clones produced fewer shoots at the 147.6 µm than at lower concentrations (1).

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A synthetic autotetraploid derived by colchicine treatment of a Vaccinium elliottii Chapm. plant (2n = 2x = 24) was used to study the effect of chromosome doubling on the ability of this noncultivated species to cross with the cultivated tetraploid highbush blueberry (V. corymbosum L.). Mean pollen germination was 28%1 for the autotetraploid plant, compared to 53% for the diploid V. elliottii plant. However, the number of seedlings obtained per flower pollinated on the tetraploid highbush cultivar O'Neal rose from 0.01 when diploid V. elliottii was the pollen source to 3.86 when pollen from the autotetraploid V. elliottii plant was used. Reciprocal crosses between diploid V. elliottii and its autotetraploid and selfs of the autotetraploid produced no seedlings. Meiotic irregularities, such as multivalent during metaphase, laggards, and unequal chromosome disjunction, were observed in the autotetraploid, but most chromosomes were associated as bivalents.

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A simple marker technique called sequence-related amplified polymorphism (SRAP) provides a useful tool for estimation of genetic diversity and phenetic relationships in natural and domesticated populations. Previous studies and our initial screen showed SRAP is highly polymorphic and more informative when compared to AFLP, RAPD and SSR markers. In this study, applicability of the SRAP markers to obtain an overview of genetic diversity and phenetic relationships present among cool-season (C3) and warm-season (C4) turfgrass species and their relationship with other Gramineae species were tested. Phenetic trees based on genetic similarities (UPGMA, N-J) were consistent with known taxonomic relationships. In some cases, well-supported relationships as well as evidence by genetic reticulation could be inferred. There was widespread genetic variation among C3 and C4 turfgrass species. In Dice based cophenetic matrix, genetic similarities among all species studied ranged from 0.08 to 0.94, whereas in Jaccard based cophenetic matrix, genetic similarities ranged from 0.05 to 0.85. C3 and C4 species were clearly distinguishable and a close relationship between italian ryegrass and tall fescue were obtained based on SRAP. Genome structures of turfgrasses are comparable to other Gramineae species. This research indicates that the SRAP markers are useful for estimating genetic relationships in a wide range of turfgrass species. The SRAP markers identified in this study can provide a useful reference for future turfgrass breeding efforts.

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